The present invention relates in general to electrodes suitable for use in arc lamps and more specifically to a one piece or unitized electrode where the final dimensions are formed by chemical etching.
In the prior art, electrodes, i.e., anodes and cathodes which are used in lamps, such as arc lamps, are generally mechanically formed. In some cases the electrodes are mechanically ground to the required tolerances and dimensions, which is labor intensive and costly. Furthermore, these mechanical forming methods result in undesirable stresses created by the electrode geometry resulting from the manufacturing process and contribute to a short lamp life. Electrodes formed in this manner are also subject when sealed in a glass envelope to cracking and/or stresses to the glass at the distal end of the anode or cathode due to a relative large geometry and sharp edges which are inherent in the forming process.
In another prior art technique, the electrode nose or head portion can be welded onto the shank portion to avoid some of the grinding requirements described above. This manufacturing technique is characterized and is the cause of embrittlement of the electrode shank when welded to form a two piece electrode, thus introducing another failure mode. The electrodes of the type described above are characterized in that they often produce streamers in the arc coming off multiple points on the edge of the electrode tip due to the manufacturing technique and geometry irregularities resulting from these methods.
It therefore can be seen that there is a need in the field for an electrode which eliminates the sharp geometry at the distal end of the electrode shank and uneven performance of the tip portion to provide and improve overall lamp life.